Ultrasharp diamond edges made from single crystal natural diamonds using special cutting and grinding methods and electron-optical control as disclosed in my U.S. Pat. Nos. 2,961,908, 3,060,781 and 3,646,841--commonly referred to as "diamond knives"--are highly useful as cutting instruments of unprecedented sharpness and also as high intensity point sources for the emission of electrons, ions and neutrons. Thus when used as cutting instruments, they are capable of molecular and submolecular sectioning at ultralow temperature in ultramicrotomy in the preparation of specimens for examination in an electron microscope. They are also useful in surgery, particularly in delicate operations such as operations on the eye. It has also been found that metals and other materials can be machined with a diamond knife to obtain a perfectly smooth surface which is free of the scratches and other imperfections resulting from usual machining and polishing operations.
When used as point sources, ultrasharp diamond edges and points in accordance with my prior patents are coated with a thin film of suitable material such as tungsten, rhenium, lanthanum, barium, caesium and other related materials of appropriate work function and physical properties for electron emission. When thus coated the ultrasharp diamond edge or point by reason of its extremely small radius (10 to 100 A) serves as a highly effective emitter for electrons, ions, x-rays, neutrons and other types of radiation.
However, the use of monocrystalline ultrasharp diamond edges and points has been limited by the cost of production and by limitations on the length of diamond edges that could be made. As high quality diamond knives are made from gem quality diamonds, the cost of such knives has accordingly been high. Moreover, by reason of larger diamonds not being available at economically acceptable prices, the length of the cutting edge of a diamond knife has been limited to less than 10 mm and is usually in the 1 to 3 mm range. As for use of diamond edges or points as cathodes or other emission electrodes, the useful life of the electrode has been limited by the dissipation of the metallic coating material. When such material has been depleted it is necessary to discard or recoat the electrode. As such electrodes are normally hermetically sealed in an appropriate envelope, the removal, recoating, remounting and resealing of the electrodes may not be economically feasible.
The limitations imposed by the size, cost and comparative rarity of suitable natural diamonds have been overcome by the production of ultrasharp polycrystalline diamond cutting edges and points as disclosed in my application Ser. No. 852,022. In accordance with the disclosure of this application, ultrasharp diamond edges and points are produced from ultrafine diamond powder by molding and bonding the powder at high temperatures and pressures in an ultrahigh vacuum or an inert atmosphere such as helium. In this manner an implement of any desired size and shape can be produced. Moreover, when the ultrasharp edge or point is to be used for electron or other emission, low work function or other emissive material in finely divided powdered form can be mixed with the diamond powder so as to be incorporated in the body of the electrode instead of being applied as a surface coating. The useful life of the electrode can thereby be greatly increased.